Organizers:
Susan Gardner
gardner@pa.uky.edu
Barry Holstein
holstein@physics.umass.edu
Jeffrey Nico
jnico@nist.gov
W. Michael Snow
wsnow@indiana.edu
Program Coordinator:
Laura Lee
lee@phys.washington.edu
(206) 685-3509
Tentative Program Schedule, with Week-by-Week Foci
Electric Dipole Moments and CP Violation Workshop
Application form
Talks online
Exit report
|
Fundamental Neutron Physics
March 19 - June 8, 2007
"Neutronic Decay" by
Dawn Meson
© 2006
The growth of neutron physics facilities worldwide
yield unprecedented
opportunities to study
the neutron's fundamental nature.
Our program plans
not only to support experiments planned at
incipient facilities, such as at the
Spallation Neutron Source (SNS), but also
to nuture new experimental and theoretical directions.
Fundamental neutron physics is naturally
of broad compass, with questions which span subfield boundaries.
We wish to bring together theorists and experimentalists
to consider and ultimately to solve problems in
topics such as we describe.
Breaking of Discrete Symmetries
The violation of
symmetries such as P, CP, and T can be studied in
a variety of low-energy processes.
Hadronic parity violation can be probed through the
study of the parity-violating asymmetry in
np→dg and through neutron spin rotation
experiments. Essential questions include what fundamental
parameters can be extracted, and
how such can be rationalized
from a rigorous non-perturbative
formulation of QCD.
The empirical bound of
the neutron electric
dipole moment (EDM) constrains
extensions of the Standard Model (SM)
with additional sources of CP violation and is relevant
to the investigation of the cosmological
problem of the baryon asymmetry of the universe.
We hope to realize a synergy of
theorists of greatly varying expertise, including
those expert in
few-nucleon and nuclear-structure physics, in effective-field-theory
techniques, in non-perturbative methods and models of QCD, as well
as those versed in building extensions of the SM,
to realize
fruitful studies of P, CP, and T
violation in hadronic systems at low energies.
CKM Unitarity and New Interactions at the Weak Scale
The focus of the neutron lifetime and neutron b-decay asymmetry
experiments is the
elucidation of the CKM matrix element Vud, to
realize, with Vus and Vub, the
world's best test of the unitarity of the CKM matrix.
The significance of this empirical test
is a crucial constraint on grand unified
theories which admit "new" physics at the TeV scale.
This is, in turn, shaped by the surety of
the "inner" radiative correction calculation which enters
the determination
of Vud from the empirical vector coupling constant gV.
We hope to foster discussion of how effective field theory techniques
employed in the study of Kl3 decay may be extended to baryonic systems,
to modernize and possibly
improve upon earlier work. Detailed measurements of the
decay correlation coefficients can also
be used to limit the presence of non-V-A weak
interactions and thus bound the presence of new weak-scale physics.
Exploring the manner in which these tests
complement precision electroweak data is of great importance.
Gravity and New Long-Range Interactions
Two disparate experiments suggest that known quantum mechanical
principles apply to gravitational potentials as well.
The first is a measurement of the gravitational phase shift
in neutron interferometry; the second is the recent inference
of gravitational bound states of ultra-cold neutrons (UCN).
The UCN results can be used to bound new long-range
interactions, which occur naturally in models with
"extra" dimensions, at the nanometer scale. Such
experiments potentially offer an interesting complement to
experiments of greater sensitivity at larger distance scales.
Understanding the role neutron experiments
can play in shaping our understanding of gravity in the quantum
regime is a topic we would like to explore.
Neutron Structure and Interactions
At low energies, the neutron's structure is probed
primarily through the
n-e scattering length, which yields the
rms charge radius of the neutron,
and electric and
magnetic polarizability measurements.
Theoretical
predictions of the neutron charge radius, be it from
lattice QCD, or from the analysis of precision atomic
and electron scattering data on the proton and deuteron, would be welcome.
The precision of low-energy n scattering experiments
to yield scattering lengths
and polarization observables have improved greatly; here
interest revolves around their theoretical interpretation
to yield insight into the NN interaction.
Nuclear Astrophysics
The measured neutron lifetime
is crucial to the predictions of big-bang nucleosynthesis (BBN)
and ultimately to understanding the manner in which the
universe has evolved throughout its history.
Here, too, effective-field-theory techniques play
a role in realizing precision predictions of key
reaction rates, such as np→dg. It would
be useful to develop a perspective on the experimental
and theoretical work yet needed to sharpen the comparison with
data as much as possible. Agreement of the predictions of
BBN with observed element abundances
can constrain the parameters of various SM extensions as well.
Spallation neutrons can also be used to generate neutrinos
and thus to study the physics of neutrino oscillations.
|